There are machines that can, at the push of a button, generate enough
magnetism to lift an automobile.

I was wondering, therefore, if it's possible to turn glue on and off.
Glue is just strong electromagnetism, isn't it?

---

Request for Question Clarification by pafalafa-ga on 28 Jul 2005 07:01 PDT

In some sense, all adhesion is a result of the electric charges of
sub-atomic particles.

Charged particles will either attract or repel one another.  When two
items, A and B -- each composed of zillions of particles -- come into
contact, if the combined attractive forces are large enough at an
atomic scale, then two items will stick together at the macroscopic
scale.

Glue helps to make this happen by getting really up close and personal
to the atomic-scale structure of both A and B, allowing gazillions
(which is a zillion, squared) of small attractions to take place,
allowing one large overall attraction that we think of as adhesion.

HOWEVER, an electromagnet that can be turned on and off is a different
creature than sub-atomic electromagentic forces, even though the two
use similar terms.  An electromagnet can indeed be turned on or off
with the flip of a switch.  But the sub-atomic, electromagetic forces
at work in glue are a permanent, built-in feature of the substance
itself.


And a good thing, too. If the sub-atomic forces could be turned on and
off at will, then we'd all be at risk of having our bodies fly apart
at any moment, since it is these same electromagnetic forces that hold
us together (even without any obvious glue).

With that as background, what sort of information would you like to
have on either electromagnets (the big ones), electromagnetic forces
(atomic scale), or glue?  Let me know, and I'll see if I can provide
an answer to your question.

Cheers,

pafalafa-ga

---

Clarification of Question by rambler-ga on 28 Jul 2005 11:48 PDT

Thank you for your very helpful response.  I just need a little
clarification (again, not too technical).

I'm not clear on the difference between the two types of
electromagnetism that you mention.

I do understand that electricity can generate magnetism, and therefore
the magnetism can be turned on and off by turning the electricity on
and off.

But what are the forces that make glue work, then, if not the same
kind of electromagnetism? Are electrons being attracted to protons, or
something like that?

Thanks again for your help.

rambler-ga,


I'm glad my brief write-up was of interest to you.  You've actually
asked a pretty fascinating question, and one that's difficult to
research, since most of the discussions of glue and adhesion don't
really venture down to the atomic-scale level.

If two objects can come very close to one another (and I mean *very*
close -- less than an atom's-width apart) then the individual atoms
often tend to bond with one another.  The bond is an electrical
phenomenon, or more broadly put, an electromagnetic phenomenon.

In theory, if I could cut a steel bar in half and produce two
perfectly smooth faces, when I put the faces back into contact, they
would adhere to one another with great force, as if they had been
super-glued.  In the real world, though, the steel faces are never
perfectly smooth, or even close to it.  There are billions of tiny
imperfections that prevent the two faces from meeting perfectly, so
that there are large (to an atom) gaps between the faces.  As a
result, they won't stick together.

But if you take two pretty flat items -- two sheets of glass, for
instance -- and sandwich them together with just a tiny bit of water,
they will stick together with amazing tenacity.  The water fills in
the gaps, and helps the glass surfaces come into close enough contact
that their own electromagnetic forces can make the two panes of glass
adhere.

The water is acting as a glue.  And this is how glue generally behaves
whenever two items are pasted together.

Here's a pretty decent write-up, that discusses the action at the atomic scale:


 
==========

http://www.studyworld.com/newsite/ReportEssay/Science/Physical%5CAdhesives-381047.htm

Adhesives

...Adhesion is the surface attraction between the surfaces of two bodies.

...The force of attraction (adhesion) is attributed to electromagnetic
interactions produced by fluctuations in the distribution of electrons
in the molecules of the facing surfaces. The distance between the
molecules of the facing surfaces is a determining factor in the amount
of force exerted. A surface that may appear smooth to the naked eye
actually may be too rough to hold its molecules close enough to a
facing surface to produce an electromagnetic bond. Gauge blocks,
pieces of metal used for taking accurate measurements, have such
smooth surfaces that their facing surfaces can be made to stick to
each other by twisting them together.


...The forces of adhesion are also used to make some very useful
products. Adhesive is a substance used to bond two or more surfaces
together. Most adhesives form a bond by filling in the minute pits and
fissures normally present in even very smooth surfaces.

==========



These forces are sometimes called electromagnetic because this term
has been used for well over a century to refer to study of electrical
and magnetic phenomena, at both macro- and micro- scales.

Here's a brief dictionary definition:




http://www.answers.com/electromagnetism&r=67

electromagnetism 

1. Magnetism produced by electric charge in motion.
2. The physics of electricity and magnetism.



Note the two different definitions.  #2 refers to the basic study of
electromagnetic forces (including those at work in glue).

But definition #1 refers to a specific effect -- the magnetism that is
generated by a moving electric charge.  This is the principle behind
the electromagnet, and the reason that an electromagnet can be turned
on and off, while the electromagnetism of glue cannot be.

Here's a link to how an electromagnet works, from the wonderful How
Stuff Works site:



http://science.howstuffworks.com/electromagnet.htm



You can see that the simple electromagnet in the diagram has a switch,
and it's the switch that can turn the magnet on and off.


The atoms in glue don't have switches, and that -- in a nutshell -- is
the big difference between electromagnets and electromagnetic forces.

Hope that's clear!  But if not, let me know if there's anything else I
can do for you.


pafalafa-ga



search strategy -- Google searches on:

glue electric OR electromagnetic forces

electromagnetism

electromagnet

Very clear and helpful answer.

Hmm.

Sniffing glue can turn you on, and then it may "off" you.

Does that count?

Glue is not electromagnetism. As far as I am aware most glues are
chemical processes.

"The glue may penetrate the pores of the material being "glued." If it
does, it can bond to the surfaces and to itself. When it hardens. the
pieces are fastened together by the strength of the material and the
strength of the glue.

Actually, there are many kinds of "glue." Not all of them work in the
same way. Some perform as described above. Others depend on a chemical
reaction that occurs between the glue and that which is being glued.
Some depend on a reaction between the glue and air or moisture on the
surfaces being glued together. Still others depend on a
reactionbetween the separate components of the glue. "

"An adhesive is a substance used to bond two or more surfaces
together.  Most adhesives form a bond by filling in the minute pits
and fissures normally present even in very smooth surfaces."

http://www.newton.dep.anl.gov/askasci/chem03/chem03289.htm

[I'm still chuckling over pinkfreud-ga's comment which, by the way,
does NOT count as an answer.]

As for scovel-ga's comment that glues are chemical processes:  well, I
remember a science program that explained that all solid objects are
solid only because of electromagnetism. "If atoms are mostly empty
space," they asked, "then why doesn't a baseball just drop right
through a catcher's mitt?" The answer, they claimed, was
electromagnetism. I think they went on to say that even glue is based
on electromagnetism (but maybe that's faulty memory on my part --
suggesting that my brain needs glue).

In any case, can we avoid the word "chemical" in the answer? Instead,
give an answer in terms of sub-atomic forces (not too technical,
though).

For example,
(1) Is glue based on electromagnetism or not?
(2) If it is, can glue be turned on and off?
(3) If not, why not?

I'll see if I can up the price on this question from $10 to $20. The
question may see frivolous (or stupid), but I'd really like an answer.

In the case of "glue", this is typically an adhesive type of material
which has hardened into a polymer state.  As such, the various
linkages set up through localized covalent bonds is what sets, or
"turns on" the glue.  To unset or "turn the glue off" requires that
the monomer state be re-established.  This can be done in a number of
ways.

For instance, a solvent can dissolve the glue, a physical,
non-chemical process ....which would likely reset again once the
solvent is re-evaporated.

Temperature can also be used to unset or "turn off" some glues.  For
some adhesive materials, an increase in temperature will provide the
vibrational kinetic energy necessary to disrupt the polymer's covalent
linkages.  Once enough of the linkages are disrupted, the adhesion
effect is minimized and the material becomes fluid-like or more
monomer-like, having little semblance to the "glue" or polymer state.

In ionic types of substances, for example magnetite, a substance which
has permanent magnetic properties, it is electrostatic forces that
hold the cations and anions together in the crystalline lattice state.
 The magnetic properties of the material generating the magnetism
effect result because of the nature of the electron configuration of
the iron cations, with no relation to the oxide ions whatsoever.

In the case of water "gluing" two pieces of glass together, this is
due to weaker, intermolecular types of bonding mechanisms, i.e.,
hydrogen-bonding, which keeps the phase contact established.  Try
replacing the two pieces of glass with two pieces of plastic and the
effect will either be nonexistent or much less present than in the
case of glass.  In the case of glass, water adhedes to the surface
because of the polarity of the functional units of the glass, (SiO_2),
and the polar nature of the water.  The glasses are each rigidly
conforming to shape by localized covalent bonds, whereas the liquid
water maintains its continuity in fluid form through the existence the
cohesively-acting, hydrogen-bonding mechanism.  These are all
electrostatic in nature and not electromagnetic.

In the case of an electromagnet, the process of creating the magnetic
field is current driven.  Without the electric current, it's off; with
the electric current, it's on.  When the electric current is on, the
moving charge creates the magnetic field which, in effect, acts at a
distance.

I do not understand the answer's connection between electromagnetism
and the cases of covalent bonding (a sharing of electrons between
nuclei), ionic bonds (an effective transfer of electrons between
nuclei yielding oppositely charged ions that become attracted), or
intermolecular bonding events (electrostatic in nature)in condensed
states.